5.8
FUEL SYSTEM
Fuel Delivery
The throttle opening chart below demonstrates component
relationship to fuel flow versus throttle valve opening.
The pilot system’s main function is that of a low speed jet. Its
most effective range of fuel delivery is from idle to
approximately 3/8 throttle valve opening.
The throttle slide controls the rate of engine air by its
movement up and down in the carburetor venturi. At small
throttle openings the air flow is regulated chiefly by the valve
cutaway, with greatest effectiveness at 1/4 throttle opening.
Throttle valves are numbered 1.0, 1.5, 2.0, etc., according to
the size of the cutaway.
Decreasing the cutaway number will increase the amount of
fuel delivered in its effective range.
The jet needle and needle jet have an effective operating range
from approximately 1/8 to 7/8 throttle opening. The amount of
fuel delivered during this range relies upon the jet needle clip
position, as well as the needle jet size and other specifications.
The main jet affects fuel delivery at 1/4 throttle and
consistently increases to full throttle opening.
Carburetor Float Bowl Draining
The carburetor float bowl should be drained periodically to
remove moisture or sediment from the bowl, or before
extended periods of storage.
NOTE: Drain screw is located on the side of the
float bowl.
1. Place a clean container beneath the bowl drain spigot or
bowl drain hose.
2. Turn the fuel valve to “OFF”.
3. Loosen drain screw and allow fuel in the float bowl and fuel
line to drain completely.
4. Inspect the drained fuel for water or sediment.
5. Tighten drain screw.
6. Turn fuel valve to “ON”.
7. Inspect carburetor for fuel leaks
8. Start machine and re-check for leaks.
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